It had been a busy Monday. Over the weekend, a German friend finished her bachelor's thesis about stone paper and asked me to print it on stone paper, logically. I was so excited by the idea, I said "yes" without any real idea of how I would do it. Stone paper is waterproof and does not take kindly to water-based inkjet inks. A big fat glob of water exploded from an electrically pulsating thermal cannon just to transport an unsightly pigment particle — ew. I am an offset boy.

At first, I thought I would do it like I did the inkjet printed letters for my first direct marketing campaigns on stone paper. Print black and white at 50% ink coverage, dry it for 10 seconds in the microwave, and hand varnish it. (That workflow took a few weeks to figure out.) The only difference between this project and those letters was that those letters had very few graphics. This essay was 24 pages of full-on text. Could you imagine the smell of pure solvent by the time she received them in a UPS package?

I told her I would do a test on Monday and get back to her. Luckily, before beginning my test today, I remembered what would become a discovery of the week. At the bottom of my filing cabinet, I had a small stack of our top-secret stone paper, with a new coating designed for inkjet printing. I had tested it previously with a full-color image from my office inkjet printer, and I was pleasantly surprised by the drying time, but the image was terrible. Since I only had it in a measly 70 gsm, my printer jammed constantly. After that first test, I condemned it to the “Chinese junk” cabinet. Anyway, I knew my Chinese partner hadn’t done much print testing. Out of laziness today, I decided to take it back out and give it another go.

The first few sheets I tried were the old stone paper sheets made for offset. I fiddled around with the ink coverage, taking the 100% K to 60% K, and okay, fine. It looked acceptable on the sheet. But like classic stone paper, it didn’t dry. One touch with my finger and it smeared. Then the thought occurred to me: If 60% ink coverage brings the dot gain under control, what happens on the new paper? Wow!

The 60% ink coverage on the new paper looked better and dried faster than my regular office paper. (The jamming is still an issue; we definitely need to get thicker paper.) I wasn’t really thinking of any larger meaning to this result when it came out, I was just thinking I could continue being lazy and still fulfill her order. But then it hit me: What if the low ink coverage was the issue from the beginning with this paper? What if it looks this good with all printed images at such low ink consumption? And that’s when my inner German printing engineer came out along with another stack of the new paper. It was time for some detailed testing!

I took a sheet of regular office paper, a sheet of offset stone paper (old), and a sheet of inkjet stone paper (new). For a fair comparison, I printed all sheets with 60% K. The ink coverage was adjusted by adjusting the opacity of the black image in Adobe InDesign. I do not have the equipment at home to make an actual ICC profile. I captured the printed images with my Sony RX 100 IV with the white balance adjusted for the marble table on my balcony in the bright sunlight. The exposure was adjusted in Adobe Lightroom to avoid black and white clipping. This is by no means an accurate test when calibrated scanners exist, but it’s better than nothing and it’s very high resolution for a large surface.

Laid side by side, the result is clear. The new paper has deeper blacks, a more pleasing white, and faster drying times without any warping whatsoever. The old paper has a more natural white, similar to the marble table made from the same mineral. The office paper has very obvious optical brighteners, showing a bluish hue. This is typical of cheap office papers that use additives to make up for a lack in quality.

As far as the blacks and whites go, I took another up-close picture of the heading on each cover page. I love looking at microscopic things. As you can see, the new stone paper is the only paper that actually has a unified black image with only 60% ink coverage. The office paper tends toward a bluish gray, and the black pigment on the old stone paper is waiting for a finger to smear it. Ignore the interference lines, my inkjet printer is not great. I actually installed a bootlegged Chinese black cartridge with 40% extra capacity, sticking it to Canon.

So far so good. This initial result with black and white is very promising. This already tells me that stone paper could compete with office paper as long as the printer is configured properly, or the office workers know how to export files with adjusted colors. The ink would surely go a longer way with this paper too. Office paper goes for a similar tonnage price as stone paper, that’s kind of cool.

After answering my German friend’s email with these test pictures, there was one more clear step to take: full-color images. Could a 60% ink coverage be the solution to the terrible images I tested earlier?

This is our base image on regular office paper, albeit while my Canon MG2540S at home was running out of color ink and I did not have a bootleg cartridge. Please cut me some slack, I usually do everything in offset. The following reference images will serve the purpose of examining the details and dot gain in the images, not the color saturation or accuracy. On every image, either the left or right side will have a blue or purple tint. Here (India.jpg) is a link to the original file.

As we can see from this image, the detail reproduction is not that great. The blacks are too dark. The dot gain is clearly an issue. Due to the high ink coverage on the paper, it came out quite soggy. But overall, it’s a recognizable image and the colors are deeply saturated.

Here is the original first test with the new stone paper in my printer. This is without any changes to the ink coverage. When I pulled this from the printer, I am pleased to say it actually dried! I watched as the huge puddles of black ink slowly dried into the new coating over the course of 10 seconds — a hugely impressive feat compared to the old stone paper. On the old stone paper, it would practically be dripping with ink. On the far right in the window you can see an area that I rubbed with my thumb. There was a lot of ink there. My thumb was black and the paper revealed its powdery surface. Needless to say, the dot gain on this image is out of control. It’s totally unacceptable. This image earned a place in the “Chinese junk” drawer, but I was wrong.

I was feeling ambitious, so first I tried a print with 50% ink coverage. Once again, I emphasize that my tiny little inkjet printer is not great, causing noticeable striping. One thing that immediately became clear: The detail reproduction was there. Look at the same place where I rubbed my thumb last time. That window grate looks great! Look at the street below and the lowlights along the buildings. They have been revealed! Based on these observations, I think we are on the right track.

If 100% is too saturated, and 50% is washed out, then 75% is the next step. Here we can see that the curve is not linear. At the 75% mark, the details are lost again, while the colors are looking similarly saturated as the office paper. This is both a good and bad result.

At this point, I only had one more sheet of our newest paper. Since it seemed the tone curve was really not linear, I tried one more value: 60% ink coverage.

If it wasn’t for the fact that I don’t have enough money to buy a new color ink cartridge, I think we are getting close to the result on office paper. In fact, considering the detail reproduction on which we are focused, we might be looking better than office paper. Even in the middle of the image, where my printer was kind enough to print somewhat full colors, the colors on the stone paper look more natural. In the lowlights, where I had plenty of black ink, it looks like more detail is visible too. Look at the rust spots on the dome at the top right — this result is very sharp.

This is where my test unfortunately had to end, because I ran out of paper and ink. After collecting all of these results, I am guessing that 66% ink coverage will produce the perfect balance between detail and color saturation.

I know this test is not exact, but it’s progress compared to what we’ve done so far. Please allow me to elaborate on what this means for stone paper’s development and why you should contact me to master printing on this material.

The production efficiency of offset stone paper is around 80%, because the thickness of blown film extrusion is relatively difficult to control. Unfortunately blown film extrusion is the only possibility for manufacturing stone paper because it gives us a competitive paper density. This tolerance adds an extra cost to a stone paper producer’s operational costs. Basically, it’s like adding an extra manufacturing expense of 20% to an already slim margin. This hidden cost has resulted in the bankruptcy of two stone paper producers in Mainland China in the last few years. If we produce stone paper for inkjet printing, for which the distance of the printing head to the substrate is more forgiving, we can achieve a production efficiency of 95%. This is much more tolerable for the newly developed equipment with which we are producing this paper. (Chinese and Taiwanese machinery so far have not been precise enough, they just aren’t there yet.)

So if we produce inkjet paper, we can produce the paper for a competitive cost and survive on our margins as well. This is a good step. But wait, there is a one-two punch to this situation that makes it seemingly unbeatable.

Look up the cost of cast coated inkjet paper. Look up the cost of HP Indigo paper. You probably see a pack of 500 13x19" in 100-lb. sheets especially coated for the HP Indigo. They cost maybe $50 USD. This is similar pricing to what we see even with lower quality Indian photo printing paper. The surface area of these sheets in metric measurements is 0.159355 sq. m. and the weight is 150 gsm. Each sheet weighs ~23.9 grams. A pack of 500 sheets weighs ~11.95 kg. That means that there are approximately 83.68 packs in one ton of paper. If you then take the tonnage price from the original $50 for the 500 sheets, you’ll get a metric tonnage price of around $4,184 USD/ton. A ton of new stone paper, which is waterproof, sustainable, bright white, soft touch, with low dot gain, costs a quarter of this.

Not only this, but a fraction of the ink is necessary to print it and achieve a similar result to traditional paper. I am confident of this conclusion, because stone paper does not absorb water or solvent like traditional paper. A 30% increase in ink efficiency seems significant in operational costs. (https://www.piworld.com/article/evaluating-total-cost-tco-inkjet-printing/)

I have taken a lot of liberties with quality and price assumptions, which is why I consider this test only to be a sign of the future circumstances. I didn’t test cast coated photo paper in a professional printer. I could have achieved a high quality result if I just made an ICC profile in a few minutes. I barely had enough ink to print 5 sheets of paper. But as you can see, we have approached an impressive result with meager printing methods on this new material. Clearly this new coating is a huge improvement on the offset stone paper, and its economics and functionality are very interesting. I personally think we have a ways to go in achieving the same quality as high quality photo paper, but we might be closer than you think.

Who is going to be the first U.S. printer to make an ICC profile for this paper and test it in their HP Indigo?

Hunter Bliss is the founder and CEO of Pebble Printing Group, a printer specializing in sustainable innovation. Pebble Printing Group is a leading innovator in stone paper material, as well other circular solutions for traditional publishing and packaging print. Hunter is from South Carolina, was educated as a printer in Germany, and founded his company in Shenzhen, China.

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